Carburetor



F. SMITH CARBURETOR Filed Feb. 25. 1935 Oct. 13, 1936.

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'CARBURETOR Filed Feb.-25 1955 2 Sheets-Sheet 2 Patented Oct. 13, 1936 OARBUBETOR Frank Smith, Huddersfield, England Application February 25, 1935, Serial No. 8,184 In Great Britain March 15, 193i 5 Claims.

The invention relates to means applied to carburetors of internal-combustion engines for the purpose of preventing waste of petrol or fuel on the closing of the throttle-valve for idling and when the engine speed is. in excess of the speed fixed for idling.

In addition to the known waste of fuel at the slow-running duct on the closing of the throttlevalve as aforesaid, it is also found that a further waste occurs owing to the building up and overflowing or ejecting of said fuel at the main fuel jet, due to vibration set up mainly from rough or uneven road surfaces which cause corresponding or abnormal fluctuations inthe seating of the float-valve.

The object of the present invention is to provide improved means applicable to the carburetor of an internal-combustion engine, whereby, on closing the throttle-valve of said carburetor when the speed of the engine exceeds the speed flxed for idling, said means is adapted to automatically operate to prevent petrol or fuel flowing to the carburetor until said engine speed becomes reduced to the idling speed, or the subsequent opening of the throttle-valve.

A further object of the invention is to provide additional means to be associated with the before mentioned means, whereby, on the closing of the throttle-valve when the engine speed exceeds the speed flxed for idling, fuel is automatically prevented from being drawn from said carburetor until the engine speed becomes reduced as aforesaid.

Other objects of the invention include the operation of said means either by a vacuum created by the engine, or by vacuum operated electrical means. Also, an improved construction of a vacuum operated valve element forming a part of the aforesaid means, provided with antifriction means, whereby, the operation of said element is rendered more sensitive and efiicient.

' In order that the invention may be more clearly understood and readily carried into effect, the same will now be described with reference to the accompanying sheets of drawings, in which:-

Figure 1 shows a side elevation, partly in section, of a fragmentary portion of a well known carburetor with the throttle-valve open and the device in its inoperative position, having a preferred form of the invention applied thereto, whereby, on closing the throttle-valve of said carburetor when the engine speed exceeds the speed fixed for idling, fuel is automatically prevented from flowing to and/or being drawn from the carburetor, until the engine assumes an idling speed or the subsequent opening of the throttlevalve. Figure 2 is a plan view of Figure 1.

Figure 3 is a sectional elevation on the line III-III of Figure 2, in the direction indicated.

Figure 4'isa similar view to Figure 1 of alternat1ve means for preventing fuel flowing to and/or being drawn from the carburetor on the closing of the throttle-valve as aforesaid.

Similar numerals refer to similar parts throughout the several views.

Referring to the drawings: construction of carburetor, 2 is the float chamber of said carburetor, receiving fuel from the customary petrol or fuel supply tank by means of pipe 3. 4 is a float-valve controlling the supply of fuel to the chamber 2. 5 is the main fuel jet,

6 the slow-running jet situated in the slow-running duct or mixing chamber 1. 8 is the known throttle-valve operated by the usual accelerator pedal, 9 is a controlled air inlet for destroying, in certain circumstances, any vacuum in the slowrunning duct'l, and I0 is a duct in which a vacuum is adapted to be formed by the engine. All these .elements form no part of the present invention and are well known in connection with carburetors of internal-combustion engines.

According to the present invention, a cylindrical casing H is provided, which may be attached to or form a part of the carburetor body I on the inlet side of the float chamber 2. The casing contains two separate valve chambers I2, I 3; a port It leading from the chamber I2 is afforded communication with the inlet 9 by means of duct I5. A second port 16 leading from the chamber I3 is afiorded communication with the float chamber 2 by means of.duct I'Lthe chamber l3 communicates with a fuel supply, not shown,

through the plug 35.

A further casing or shell [8 is secured to or forms an extension of the casing H, which has a portion l9 cut away in cylindro-conoidal fashion which constitute an auxiliary air chamber. Openings 20 are formed in the wall of the casing l8 and are protected by a reticulatedscreen 2| which is also adapted to filter the air as it passes through said openings into the chamber l2.

A spring-loaded piston valve of preferably two, diameters 22, 23, is employed within the shell l8 and inner and outer valve seats 24' at the top of said chamber l2 are engaged by the reduced end 23 of said piston valve to exclude atmospheric air from passing into the chamber 12 and by way of duct 15 into the chamber 1.

A further valve 25 operating in chamber l3 and I is awell knownan insulated contact 4 l provided with a-stem, or, an extension 26 is arrangedto engage the part 23, and is adapted in normal circumstances, to be held off its seat 21 by the said part. 23 or an extension thereof when the part 23 is in engagement with the seats 24, and to be raised by a spring 28 on to the seat 21 when part 23 is out of engagement with said seats 24. The inner seat 24 also prevents leakage of petrol past the extension or stem 26 during normal conditions.

Antifriction means such as ball-bearings 29 are provided between the end 23 of the said piston valve and the spring 30 associated therewith, which prevent, on the compression or expansion of the spring 30, any tendency on the part of the piston valve to angular movement, and is adapted to eliminate any friction between the valve casing 18 and the valve, whereby, the latter is rendered more sensitive and efficient.

3! are adjusting means provided or associated with the piston valve, in order that the degree of vacuum required to operate the said valve, may be varied to suit requirements.

During normal running of the engine (see Figures 1, 2, and 3 of the drawings), the several elements comprising the invention remain inoperative with fuel flowing to the carburetor in the usual manner and atmospheric air shut off from the slow running duct or mixing chamber I. On closing the throttle-valve 8 when the engine speed exceeds the speed fixed for idling, the increase in vacuum in the duct [0 is communicated to the chamber 32 and acts on the piston valve to raise the part 23 off the seats 24.

The raising of the piston valve as aforesaid,

enables the spring 28 to raise the valve 25 on to its seat 21, interrupting further flow of fuel to the float chamber 2. Simultaneously, the raising of the part 23 as aforesaid uncovers the openings 20 in the casing i8, admitting air to chamber I 2 from which it passes through port I, duct l5 and inlet 9, to the slow-running duct or mixing chamber"! to destroy any vacuum which may have been formed therein, thus preventing any fuel being drawn from the carburetor.

Immediately the speed of the engine becomes reduced to that fixed for idling or when the throttle valve is-opened, the vacuum in duct I 0 has become correspondingly weakened, whereupon the spring 30 returns the piston valve on to the seats 24, thereby interrupting the flow of air to chamber 1, and moving valve 25 off its seat 21 to again permit the flow of fuel to the float chamber 2.

With reference to Figure 4 of the drawings, the piston valve before described may be dispensed with and an electro-magnet or solenoid substi-- tuted therefor, for interrupting the flow of fuel and for admitting air as before described.

For this purpose, the solenoid 36 is secured to casing II in the manner of the casing l8, and the solenoid plunger 31 on the completion of an electric circuit is raised off the seats 24 enabling spring 28 to raise valve 25 into engagement with seat 21 and interrupt the flow of fuel to chamber 2 as before described. The raising of plunger 31 as aforesaid also affords communication with chamber i2 to admit air to chamber 1 by way of port I4 and duct ii for the purposes before described.

. 38 is a battery, and in the electric circuit thereof is a switch 39 within'a casing 40, provided with The bottom of the chamber 32' in the casing 40 is afforded communication with the carburetor bore on the engine side of the throttle valve by means of the duct It, so that,

With reference to the application of the invention to the controllable jet or constant vacuum type of carburetor where no slow running fuel duct or mixing chamber 1 is provided, fuel is prevented from flowing to the carburetor in the manner and by the means before described while air is simultaneously admitted into the carburetor bore between the fuel jet and' the throttle-valve, to destroy any vacuum that may be formed therein for preventing fuel being drawn from said jet when the throttle-valve is closed and the engine speed exceeds the speed fixed for idling as before described,- in which case this part of the carburetor bore receiving said air functions as the equivalent of the fuel duct in static carburetors where slow-running fuel jets or ducts are provided.

What I claim as my invention, and desire to secure by Letters Patent, is:--

1. In combination with a carburetor, of means positioned in the fuel supply passage of the carmunicating with the atmosphere and provided with a port arranged to communicate with the air chamber, a reciprocating piston valve for I controlling said port, said-air chamber having a valve seat for receiving said piston valve, a spring supported valve in said fuel chamber for controlling the supply of fuel to the float chamber, said spring valve having its stem extending so as to engage the piston valve, said piston valve normally maintaining the spring valve *open to permit the flow of fuel to the float chamber and also closing communication of the air chamber with the auxiliary air chamber, and means operatively connecting the piston valve to the carburetor bore whereby upon the closing of the throttle valve when the speed exceeds the speed fixed for idling, the vacuum created in the carburetor bore by the excessive speed, operates the piston valve so as to raise it'off of its seat to permit atmospheric air to pass into the air chamber and the carburetor bore and to simultaneously move the spring valve to close the flow of fuel to the carburetor until the engine speed is reduced to the idling speed or the throttle valve is opened.

2. In combination with a carburetor, of means positioned in the fue supply passage of the carburetor for preventing the waste of fuel, said means including a valve body having a fuel chamber and a separate air chamber, means communicating the air chamber with the slow running duct of the carburetor, means communicating the fuel chamber with the float chamber of the carburetor, a casing attached to said valve body and provided with an auxiliary air chamber, said auxiliary air chamber communicating with .the atmosphere and having a port arranged to communicate with the air chamber, a solenoid poppet valve in said casing for controlling the supply of air through said port, said air chamber having a valve seat for receiving said poppet valve, a spring supported valve in said fuel chamber for controlling the supply of fuel to the float chamber, said spring valve having its stem extending upwardly so as to engage the poppet valve adjacent its valve seat, said piston valve normally maintaining the spring valve open to permit the flow of fuel to the float chamber and also closing communication of the air chamber with the auxiliary air chamber, a supplemental casing communicating with the carburetor bore, a plunger switch and a terminal contact in said supplemental casing, and means electrically connecting said switch with said poppet valve, whereby on the closing of the throttle valve when the engine speed exceeds the speed fixed for idling, the vacuum created in the carburetor bore by the excess speed. operatesthe switch in the supplemental casing so as to engage said contact and completes an electric circuit which raises the poppet valve off of its seat and por mits atmospheric air to pass to the slow running duct and simultaneously closes the spring supported valve so as to prevent fuel flowing to the carburetor until the engine speed is reduced to the idling speed or the throttle valve is opened.

3. In combination with a carburetor, of means positioned in the fuel supply passage of the carburetor for preventing the waste of fuel, said means including a valve body having a fuel chamber and a separate air chamber, means communicating the air chamber with the carburetor bore, means communicating the fuel chamber with the float chamber of the carburetor, said valve body having an auxiliary air chamber communicating with the atmosphere and provided with a port arranged to communicate with the air chamber, a reciprocating piston valve for controlling said port, anti-friction means .associated with the piston valve for preventing angular movement of the latter, said air chamber having a valve seat for receiving said piston valve, a spring supported valve in said fuel chamber for controlling the.supply of fuel to the float chamber, said spring valve having its stem extending so as to engage the piston valve adiacent its valve seat, said piston valve normally maintaining the spring valve open to permit the flow of fuel to the float chamber and also.

closing communication of the air chamber with the auxiliary air chamber, and means operatively connecting the piston valve to the carburetor bore whereby upon the closing of the throttle valve when the speed exceeds the speed flxed for idling, the vacuum created in the carburetor bore by the excessive speed operates the piston'valve so as to raise it off of its seat to permit atmospheric air to passinto the air chamber and the carburetor bore and to simultaneously move the spring valve to close the flow of fuel to the carburetor until the engine speed reduces to the idling speed or the throttle valve is opened.

4. In combination with av carburetor, of means pdsitioned in the fuel supply passage of the carburetor for preventing the waste of fuel, said means including a valve body having a fuel chamber and a separate air chamber, means communicating the air chamber with the slow running duct of the carburetor, means communicating the fuel chamber with the float chamber of the carburetor, a.casing attached to said valve body and provided with an auxiliary air chamber, said auxiliary air chamber communicating with the atmosphere and having a port arranged to communicate with the air chamber, a reciprocating piston valve mounted in said casing for controlling the supply of air through said port, said piston' valve having two diameters with its smaller diameter disposed adjacent said ports, a spring supported valve in said fuel chamber for control-' ling the supply of fuel to the float chamber, said spring valve having its stem extending so as to engage the piston valve, said piston valve normally maintaining the spring valve open to permit the flow of fuel to the float chamber and also closing communication of the air chamber with the auxiliary air chamber, andm'eans operatively connecting the piston valve to the carburetor bore whereby upon the closing of the throttle valve when the speed exceeds the speed fixed for idling, the vacuum created in the carburetor bore by the excessive speed, operates the piston valve so as to raise it off of its seat to permit atmospheric air to pass into the air chamber and the carburetor bore and to simultaneously move the spring valve the throttle valve is opened. I

5. In combination with a carburetor, of means positioned in the fuel supply passage of the carburetor' for preventing the waste of fuel, said means including a valve body having a fuel chamber and a separate air chamber, means communicating the air chamber with the carburetor bore. means communicating the fuel chamber with the float chamber of the carburetor, said valve body having an auxiliary air chamber communicating with the atmosphere andprovided with a port arranged to communicate with the air chamber,

means operatively connecting the reciprocating member'to the carburetor bore whereby upon the closing of the throttle valve when the speed exceeds the speed fixed for idling, the vacuum created in the carburetor bore by the excessive speed, operates the piston valve so as to raise it ofi of its seat to permit atmospheric air to pass into the air chamber and the carburetor bore and to simultaneously move the spring valve to close the flow of fuel to the carburetor until the engine,

speed is reduced to the idling speed or the throttle valve is opened. If'RANK SMITH. 

